Pass hash to subroutine inside a subroutine already passed that hash - perl

Question

I am working with passing hashes to various subroutines, and I was wondering how to pass a hash to a subroutine and then pass the same hash inside that subroutine to a different subroutine and so on.
For example, the following code works fine.
use strict;
use warnings;
my %hash = (
key1 => 'value1',
key2 => 'value2',
key3 => 'value3',
key4 => '',
);
print %hash, "\n";
check_it(\%hash);
sub check_it {
my $params = shift;
foreach(keys %{$params}){
if($params->{$_}) {
print "'$_' defined as '$params->{$_}'\n";
}
else {
print "'$_' not defined as '$params->{$_}'. Deleting it.\n";
#delete $params->{$_};
$params->{$_} = 'null';
}
}
for ( my $i = 0 ; $i < 7 ; $i++ ) {
print "looping\n";
&check_tags_again(\%hash);
}
}
sub check_tags_again {
my $hash_now = shift;
#check again...
foreach(keys %{$hash_now}){
print "An element of hash: ", $hash_now->{$_}, "\n";
#if(defined $hash_now->{$_}){ delete $hash_now->{$_};}
}
&check_tags_thrice(\%hash);
}
sub check_tags_thrice {
my $hash_now = shift;
#check again...
foreach(keys %{$hash_now}){
print "An element of hash: ", $hash_now->{$_}, "\n";
#if(defined $hash_now->{$_}){ delete $hash_now->{$_};}
}
}
print "final hash:", %hash, "\n";
BUT, when I run the code that follows:
use strict;
use warnings;
use Data::Dumper;
sub process_data {
my $group_size = 10;
my %HoA = (
flintstones => [ "fred", "barney" ],
jetsons => [ "george", "jane", "elroy" ],
simpsons => [ "homer", "marge", "bart" ],
);
&delete_stuff( \%HoA, $group_size );
print "New group:\n";
print Dumper( \%HoA );
undef %HoA;
}
sub delete_stuff {
my $HoARef = shift;
my $group_size = shift;
print "group size in sub $group_size\n";
for ( my $j = 0 ; $j < $group_size ; $j++ ) {
my $dlted = &delete_other_stuff( \%HoA, $j );
print "deleted? '$dlted'\n";
if ( $dlted == 0 ) {
&presence_check( \%HoA, $j );
}
for ( my $i = 0 ; $i < $group_size ; $i++ ) {
}
}
}
sub delete_other_stuff {
my $HoAref = shift;
my $Dex = shift;
return $deleted;
}
sub presence_check {
my $HoAreF = shift;
my $DeX = shift;
}
I get:
Global symbol "%HoA" requires explicit package name at x.pl line 32.
Global symbol "%HoA" requires explicit package name at x.pl line 35.
Execution of x.pl aborted due to compilation errors.
I'm confused because I think it's doing the same thing as the first, but now it claims that %HoA was never initialized.

Answer 1

In delete_stuff, you don't have %HoA, you have $HoARef. If all the subs are expecting a reference to a hash, then you can just use it:
for ( my $j = 0 ; $j < $group_size ; $j++ ) {
my $dlted = &delete_other_stuff( $HoARef, $j );
print "deleted? '$dlted'\n";
if ( $dlted == 0 ) {
&presence_check( $HoARef, $j );
}
...
}
By the way, we're closing on 20 years of Perl 5. There is no reason to call a sub with explicitly passed parameters with an &, which is a Perl 4 holdover.